System for overcoming dead center in reciprocating engines



Nov. 4, 1958 P. H. SCHNEIDER SYSTEM FOR OVERCOMING DEAD CENTER IN RECIPROCATING ENGINES Filed Feb. 3, 1956 2 Sheets-Sheet l jrzvemon' PAl/l. b! SCHNEIDER Nov. 4, 1958 P. H. SCHNEIDER v2,353,70?

SYSTEM FOR OVERCOMING DEAD CENTER IN RECIPROCATING ENGINES 2 Sheets-Sheet 2 Filed Feb. 3, 1956 jm/emart' PAUL Ii SLH/VE/DER I Zr 73a Q 7 WA GENT United States Patent Q SYSTEM FOR OVERCUMIVG DEAD CENTER 1N REQEFRUCATHNG ENGINES Paul Hermann Schneider, Frankfurt am Main, Germany Application February 3, 1956, Serial No. 563,356

Claims priority, application Germany February 9, 1955 3 Claims. (Cl. 74-36) My present invention relatesto a system for overcoming dead center in prime movers using reciprocating pistons, such as steam engines or internal-combustion engines.

In conventional machines of this character, the crank shaft coulpled with the piston rod reaches dead center simultaneously with the piston arriving at an extereme position of its travel. Since such systems are likely to come to a stop at or near one of these extreme positions, re-starting is often difiicult or impossible without the application of an extraneous force.

An object of this invention is, accordingly, to provide an arrangement for so displacing the dead-center position of reciprocating engines as to have them occur at some intermediate point of the piston stroke.

Another'object of my invention is to provide an arrangement of the character described in which the path traveled by the crank and of the piston rod, bearing the usual cross head, is greater during the working stroke of the piston than during the return stroke whereby a more favorable torque distribution is obtained.

In accordance with the present invention, the cross head of the piston rod is connected not directly to the crank of a driven shaft but to an extremity of a pitman which in turn is linked with the crank at a point whose distance from the cross head is preferably less than the eccentricity of the crank; the other extremity of the pitman intersects a line which passes through the axis of the crank shaft and is at least roughly perpendicular to the axis of the piston cylinder, being constrained to swing about a point located on said line.

A particularly advantageous embodiment of my invention comprises a pair of parallel crank shafts whose as sociated pitmans are telescoped together or otherwise interconnected for relative displacement in an axial direction only; if the two shafts carry gears or equivalent means positively coupling them for rotation at the same speed but in opposite directions, the two pitmans will mutually serve as means for causing each other to oscillate about a point located between said shafts.

The above and other features of the invention will become more fully apparent from the following detailed description of certain embodiments, reference being bad to the accompanying drawing in which:

Fig. 1 is a side elevational View of a conventional crank directly coupled with a piston rod;

Fig. 2 is a top plan view of the crank shown in Fig. 1;

Fig. 3 is a view similar to Fig. 1 but showinga crank coupled to a piston rod through the intermediary of a pitman, in accordance with the'present invention;

Fig. 4 is a top plan view of the crank-pitman assembly of Fig. 3;

Fig. 5 is a view similar to Fig. 3 but showing the system at a different phase of its operative cycle;

Fig. 6 is another view similar to Fig. 3 but illustrating additional parts of a system embodying the invention;

Fig. 7 shows a partial modification of the system of Fig. 6;

Fig. 8 is a side-elevational view of another embodiment of the invention; I

Fig. 9 is a view similar to Fig. 8, showing a further development of the system of-Fig. 8; r

Fig. 10 is a side-elevational view of still another embodiment;

Fig. 11 is a view similar to Fig. 4 but showing a double-crank assembly according tothe invention;

Fig. 12 is a side-elevational view of a two-piston system utilizing the assembly of Fig. 11;

Fig. 13 is a view similar to Fig. 12, showing a further development with four pistons;

Fig. 14 is a view similar to Fig. 11, showing a modified double-crank assembly;

Fig. 15 is a view similar to Fig. 12, showing a twopiston system utilizing the assembly of Fig. 14; and

Fig. 16 is a side-elevational view of a triple-crank arrangement representing a further development of the system of Fig. 6.

Figs. 1 and 2 show a conventional crank 1 secured by a crank pin 3 to the cross head of a piston'rod 4, the latter reciprocating in a piston cylinder not shown. The path of crank pin 3 is circular and has been illustrated at e. The crank shaft is shown at 11.

In Figs. 3 and 4 I have'shown the samepiston rod 4 secured by its pin 3 to a pitman 2, the latter being coupled with crank 1 by means of a pin 28 whose spacing from pin 3 is slightly less than'the eccentricity of'the crank, i. e.. the spacing between the axes of pin 28 and shaft 11. The direction of rod in Figs. 1 and 3 is nearly vertical, this being also the approximate direction of the axis of the piston cylinder (not shown). The lefthand extremity of pitman- 2, opposite the extremity27 guided for sliding movement along the-aforementioned horizontal line which has ben indicated at 38.

The arrangement of Fig. 3 is suchthatthe length of its piston stroke -is the same as in the conventional system of Fig. 1, the orbit e of pin 3 in Fig. 1 having also been shown in Fig. 3 for purposes of comparison. Thus it will be seen that crank pin 28 in Fig. 3 describes an orbit 29 which is somewhat less in radius than orbit-e; at the same time the eccentricity of pin 3, in the position illustrated in Fig. 3, is greater than at any point in the arrangement of Fig. 1. The two dead-center positions, occurring when crank 1 is parallel to red 4, havebeen indicated at .30 and 31. The pin 3 reaches its highest and its lowest point in the two positions in which the crank 1 isperpendicular to line 38; it is a relatively simple matter to offset the piston cylinder in the direction of shaft 11 from a point directly above the top position of pin 3 (as shown in subsequent figures) so that rod 4 will be inclined at this point in a sense tending to urge pin 3 onto the right-hand portion 17 of'its travel. It will be noted that the path 17 between points 30 and 31 is longer than the return path .18, the eccentricity of pin 3 along path 17 being greater than in the arrangement of Fig. 1 whereby a'greater-torque will be'exerted. upon g and g on both sides of the midpoint h of path 18. At

points h and h; the pin 3 travels at the same intermediate speed; also, its speed at the nadir i is the same as as the zenith i In the case of internal-combustion engines, therefore, it will be dsirable to incline the axis of the piston cylinder (e. g. as shown in Fig. 8) in such manner that the same is more nearly tangential to path 17 at the location 1, as by being approximately tangent to the orbit 29 of crank pin 28. Under these circumstances the first portion of the explosion stroke, at which the greatest amount of power is developed, will occur in the most favorable position of members 1, 2 and 4. It may be mentioned, however, that an increase in torque in comparison with the system of Fig. 1 will also occur at point h whereby enhanced efiiciency will also be obtainable in the case of steam engines, compressed-air motors and other reciprocating engines in which power is applied to the piston on every stroke.

In Fig. 6, where a complete system including piston 5 and cylinder 6 is illustrated, I have shown pivot pin 37 I as the axle of a roller 7 movable, with small clearance,

between a pair of horizontal guide rails 8 in order to insure sliding motion of pivot 37 along line 38 (Fig. 3). In Fig. 7 the roller 7 has been replaced by an auxiliary piston slidable in a piston cylinder 9 having an orifice 39 through which air, water or some other fluid, aspirated through another orifice (not shown), may be delivered; piston 10 thus operates as a pump or a compressor while simultaneously affording proper guidance to pitman 2.

Fig. 8 shows an arrangement in which a second crank 1', parallel and opposite to crank 1, is mounted on a shaft 11' which is parallel to shaft 11. A pair of arms 13 and 14, pivotally linked to cranks 1 and 1 at'28 and 28', respectively, replace the pitman 2 of the preceding figures; they are slidably interconnected by a reduced extension 15 of arm 14 which is telescoped in arm 13. The parallelism between cranks 1 and 1 is maintained by a pair of meshing gears 16, 16' on shafts 11 and 11'.

It will be seen that opposite extremities of the telescoped unit 1315 describe paths which are similar to the orbit 17, 18 of pin 3 in Fig. 3. The fulcrum of the double pitman 13, 14 remains fixed at the midpoint between shafts 11 and 11', the second degree of freedom being provided by the extensibility of this unit. Fig. 9 shows an arrangement in which both of the aforementioned extremities are linked, by means of pins 3 and 3 engaging rods 4 and4, to respective pistons 5 and 5' sliding in cylinders 6 and 6'.

It will be appreciated that Figs. 6 and 8 are representative of arrangements in which any number of cylinders 6 are positioned behind one another and coupled with shaft 11, and that similarly Fig. 9 is representative of an arrangement comprising two rows of cylinders 6 and 6. The invention is, however, also applicable to systems in which two or more cylinders diverge radially with respect to a shaft, one such system having been illustrated in Fig. 10 where two piston rods 4 and 4', extending in opposite directions, engage the same pin 3. Only a single shaft 11 is shown in Fig. 10, yet the pitman there again has the form of a telescoped unit 1315 whose fulcrum 37 is fixed to the frame of the machine (not shown).

In Fig. 11 I have shown a pair of rigidly interconnected cranks 23, 23 to which a pair of pitmans 2, 2

12 in which the pivot pins 37, 37' at the ends of the 4 long lever arms of pitmans 2, 2 form journals for a pair of rollers 7, 7 displaceable between respective guide rails 8, 8'. A pair of piston rods 4, 4' are linked to pitmans 2, 2' at 3 and 3, respectively.

In Fig. 13 the system of Fig. 12 has been modified by replacing each pitman 2, 2 with a respective telescoped unit 13, 14, 15 and 13, 14, 15 having fixed fulcrums 37 and 37'. As in the arrangement of Fig. 10, two piston rods 4a, 4b and 4a, 4b are respectively connected to each pitman at 3, 3; the associated piston cylinders have been designated 6a, 6a and 6b, 612.

Fig. 14 differs from Fig. 11 in that the two rigidly interconnected cranks, here designated 22 and 22, have been relatively offset around shaft 11 by An embodiment utilizing this arrangement has been shown in Fig. 15 in which, in the position illustrated, pitman 2 completely obscures its 'mate 2'. The guide means 8, 8' for the two pitmans are the same as in Figs. 6 and 12.

The arrangement shown in Fig. 16 is particularly adapted for use in locomotives. The rod 4, emerging from steam cylinder 6, is coupled via a cross head 40 to a link 41, the latter in turn engaging the first one of three pivot pins 3, 3, 3" forming junctions between a connecting rod 25 and respective pitmans 2, 2, 2". These pitmans are pivoted onto cranks 1, 1', 1" on shafts 11, 11, 11", respectively, and their other extremities are slidably guided for parallel movement transverse to rod 25 by rails 8, 8, 8 in line with the respective shafts. The wheels of the locomotive have been illustrated at 42, 42', 42".

Many modifications, adaptations and combinations of the features described above and shown in the drawing are possible without departing from the spirit and scope of the appended claims.

I claim:

1. In a prime mover, in combination, a first and a second driven shaft parallel to one another, gear means on said shafts interconnecting same for simultaneous rotation at equal angular velocities and in opposite directions, a first and a second crank parallel and diametrically opposite to each' other and secured, respectively, to said first and second shafts for rotation therewith, a first and a second pitman having adjacent extremities telescoped together and having free ends with first and second pivot means respectively linking them to said first and second cranks, a cylinder, a driving piston reciprocable within said cylinder, and a rod having one end connected to said piston and having at its other end a cross head connected to the free end of said first pitman at a point beyond said first pivot means.

2. The combination according to claim 1, further comprising a second cylinder and a second driving piston reciprocable within said second cylinder, and a second rod having one end connected to said second piston and having at its other end a second cross head connected to the free end of said second pitman at a point beyond References Cited in the file of this patent UNITED STATES PATENTS 1,506,626 Freer Aug. 26, 1926 Freer Oct. 7, 1919' 

